Real-World Experience of Palbociclib-Induced Adverse Events and Compliance With Complete Blood Count Monitoring in Women With Hormone Receptor–Positive/HER2-Negative Metastatic Breast Cancer

Abemaciclib increases the risk of venous thromboembolism in breast cancer: Integrate meta-analysis, pharmacovigilance database analysis, and in vitro validation

BACKGROUND

Recently, cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) have emerged as a novel treatment strategy for breast cancer. However, increasing reports of CDK4/6i-associated venous thromboembolism (VTE) have garnered attention. This study assessed CDK4/6i-associated VTE in breast cancer, and examined the effect of CDK4/6i on platelet/coagulation function for the first time in vitro.

METHODS

PubMed and Embase databases were searched for studies published from the establishment of the database to December 31, 2022 for randomized controlled trials (RCTs) and real-world studies of CDK4/6i in patients with breast cancer, and the data obtained from the included studies were used for meta-analysis. A disproportionality analysis by extracting adverse drug reaction signals of CDK4/6i-associated VTE from the FDA Adverse Event Reporting System (FAERS) database was also conducted. Additionally, the in vitro effect of CDK4/6i on platelet function was assessed based on platelet aggregation tests and flow cytometry, and coagulation function was assessed based on the blood clotting function test.

FINDINGS

A total of 16,903 patients in 13 RCTs and 6,490 patients in 9 real-world studies were included in the meta-analysis. In RCTs, VTE occurred in 193 (2.1 %) and 55 (0.7 %) patients in the CDK4/6i and control groups, respectively. In real-world studies, the aggregate incidence rate of VTE was 4.2 % (95 % CI: 2.1, 6.3). The meta-analysis of RCTs revealed that abemaciclib (Odds ratio [OR]: 4.40 [95 % CI: 2.74,7.05], p < 0.001) and palbociclib (OR: 2.35 [95 % CI: 1.34, 4.12], p < 0.01) significantly increased the risk of VTE in patients with breast cancer compared to placebo. FAERS database analysis revealed that abemaciclib (reporting odds ratio [ROR]: 1.63 [95 % CI: 1.36, 1.97]; IC025: 0.67) and ribociclib (ROR: 1.17 [95 % CI: 1.0, 1.39]; IC025: 0.18) demonstrated a significantly increased signal of VTE. Similarly, findings from in vitro experiments demonstrated that abemaciclib enhanced agonist-induced platelet activation, especially when collagen was used as the inducer, and this effect became more prominent with increasing its concentration.

INTERPRETATION

Use of abemaciclib may increase the risk of VTE in patients with breast cancer, which may be partially attributed to the effect of abemaciclib on platelet function. Close monitoring of VTE occurrence is highly recommended while using abemaciclib, especially in patients at a high risk of VTE.

Thrombosis in breast cancer patients on cyclin-dependent kinase inhibitors: Survival impact and predictive factors - A study by the cancer and thrombosis group of the spanish society of medical oncology (SEOM)

Thrombosis may be included in the profile of side effects associated with CDK4/6 inhibitors. Its significance might be greater than reported in randomized clinical trials. To investigate this, a retrospective, multicenter study was conducted. The primary objective was to calculate the incidence of thrombosis associated with CDK4/6 inhibitors. Secondary objectives included examining the impact of thrombosis on survival and identifying predictor variables for the development of venous thromboembolism (VTE) or arterial thrombosis (AT). A total of 986 patients were recruited. The incidence of VTE/AT associated with CDK4/6 inhibitor treatment during the follow-up period was 5.48 %. Survival analysis did not indicate that the development of VTE/AT during CDK4/6 inhibitor treatment significantly impacted patient survival (p = 0.133). In our analysis, two variables were found to be statistically significant (p < 0.05) as predictors of VTE/AT in breast cancer patients receiving CDK4/6 inhibitor therapy. These variables were the presence of central nervous system (CNS) metastasis with an odds ratio (OR) of 3.68 (95 % CI 1.18 - 11.49) and the use of abemaciclib with an OR of 2.3 (95 % CI 1.16 - 4.57).

First-line therapy with palbociclib in patients with advanced HR+/HER2- breast cancer: The real-life study PALBOSPAIN

PURPOSE

To evaluate the efficacy and safety of first-line therapy with palbociclib in a Spanish cohort treated after palbociclib approval.

METHODS

PALBOSPAIN is an observational, retrospective, multicenter study evaluating real-world patterns and outcomes with 1 L palbociclib in men and women (any menopausal status) with advanced HR+/HER2- BC diagnosed between November 2017 and November 2019. The primary endpoint was real-world progression-free survival (rw-PFS). Secondary endpoints included overall survival (OS), the real-world response rate (rw-RR), the clinical benefit rate, palbociclib dose reduction, and safety.

RESULTS

A total of 762 patients were included. The median rw-PFS and OS were 24 months (95% CI 21-27) and 42 months (40-not estimable [NE]) in the whole population, respectively. By cohort, the median rw-PFS and OS were as follows: 28 (95% CI 23-39) and 44 (95% CI 38-NE) months in patients with de novo metastatic disease, 13 (95% CI 11-17) and 36 months (95% CI 31-41) in patients who experienced relapse < 12 months after the end of ET, and 31 months (95% CI 26-37) and not reached (NR) in patients who experienced relapse > 12 months after the end of ET. rw-PFS and OS were longer in patients with oligometastasis and only one metastatic site and those with non-visceral disease. The most frequent hematologic toxicity was neutropenia (72%; grade ≥ 3: 52.5%), and the most common non-hematologic adverse event was asthenia (38%).

CONCLUSION

These findings, consistent with those from clinical trials, support use of palbociclib plus ET as 1 L for advanced BC in the real-world setting, including pre-menopausal women and men.

TRIAL REGISTRATION NUMBER

NCT04874025 (PALBOSPAIN). Date of registration: 04/30/2021 retrospectively registered.

A pharmacist-led interprofessional medication adherence program improved adherence to oral anticancer therapies: The OpTAT randomized controlled trial

BACKGROUND

Oral anticancer therapies such as protein kinase inhibitors (PKIs) are increasingly prescribed in cancer care. We aimed to evaluate the impact of a pharmacist-led interprofessional medication adherence program (IMAP) on patient implementation (dosing history), persistence (time until premature cessation of the treatment) and adherence to 27 PKIs prescribed for various solid cancers, as well as the impact on patients' beliefs about medicines (BAM) and quality of life (QoL).

METHODS

Patients (n = 118) were randomized 1:1 into two arms. In the intervention arm, pharmacists supported patient adherence through monthly electronic and motivational feedback, including educational, behavioral and affective components, for 12 months. The control arm received standard care plus EM without intervention. All PKIs were delivered in electronic monitors (EMs). Medication implementation and adherence were compared between groups using generalized estimating equation models, in which relevant covariables were included; persistence was compared with Kaplan‒Meier curves. Information on all treatment interruptions was compiled for the analysis. Questionnaires to evaluate BAM and QoL were completed among patients who refused and those who accepted to participate at inclusion, 6 and 12 months post-inclusion or at study exit.

RESULTS

Day-by-day PKI implementation was consistently higher and statistically significant in the intervention arm (n = 58) than in the control arm (n = 60), with 98.1% and 95.0% (Δ3.1%, 95% confidence interval (CI) of the difference 2.5%; 3.7%) implementation at 6 months, respectively. The probabilities of persistence and adherence were not different between groups, and no difference was found between groups for BAM and QoL scores. No difference in BAM or QoL was found among patients who refused versus those who participated. The intervention benefited mostly men (at 6 months, Δ4.7%, 95% CI 3.4%; 6.0%), those younger than 60 years (Δ4.0%, 95% CI 3.1%; 4.9%), those who had initiated PKI more than 60 days ago before inclusion (Δ4.5%, 95% CI 3.6%; 5.4%), patients without metastasis (Δ4.5%, 95% CI 3.4%; 5.7%), those who were diagnosed with metastasis more than 2 years ago (Δ5.3%, 95% CI 4.3%; 6.4%) and those who had never used any adherence tool before inclusion (Δ3.8%, 95% CI 3.1%; 4.5%).

CONCLUSIONS

The IMAP, led by pharmacists in the context of an interprofessional collaborative practice, supported adherence, specifically implementation, to PKIs among patients with solid cancers. To manage adverse drug events, PKI transient interruptions are often mandated as part of a strategy for treatment and adherence optimization according to guidelines. Implementation of longer-term medication adherence interventions in the daily clinic may contribute to the improvement of progression-free survival.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04484064.

Real-world effectiveness of ribociclib in metastatic breast cancer patients: Does dose affect survival?

Introduction: Real-world data are critical to demonstrate the reproducibility of evidence and external generalizability of randomized clinical trials. The purpose of this study was to assess real-world security profile and management of adverse events (AEs) presented with ribociclib for the treatment of HR + /HER2- metastatic breast cancer (MBC). Our secondary objective was to provide real-world effectiveness of this treatment (measured with progression-free survival (PFS)) and to confirm the hypothesis that dose reductions are not related with disease progression. Material and methods: Observational retrospective study evaluating all females with MBC treated with ribociclib. Study period: January 2017 to September 2019. Follow-up was done until November 2021. Response was assessed through the PFS according to RECIST1.1 and National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) was used to classify AEs. Results: The most common AE was any grade neutropenia, documented in 37 of 53 patients (69.8%) during the course of treatment. By the end of the follow-up period, overall median PFS with ribociclib therapy was 27.3 months (95% confidence interval (CI) 20.8-71.8 months). In total, 50 patients (94.4%) initiated ribociclib at 600 mg dose, 28 patients (58%) required dose reductions. PFS of patients receiving ribociclib as first-line treatment was 28 (95% CI 15-41 months). Conclusions: Our results from patients treated in real-world clinical settings indicate that ribociclib is safe and their AEs are manageable with active monitoring, temporal suspension of treatment and dose reduction. Furthermore, our results indicate that dose reduction of ribociclib is not associated with a loss of efficacy.

Cyclin-dependent kinase 4/6 inhibitor-associated thromboembolism: a critical evaluation of the current evidence

Cyclin-dependent kinase 4/6 (CDK 4/6) inhibitors are an essential treatment modality for hormone receptor-positive breast cancer. As the rates of breast cancer continue to rise globally and the indications for CDK 4/6 inhibitors now extend beyond metastatic disease, more patients than ever are receiving these agents. Thrombosis is an emerging clinical concern with this class of agents, particularly venous thromboembolism. Although venous thromboembolism initially emerged as an adverse effect of interest in early trials, more recent studies have demonstrated even higher incidences of thrombosis in real-world clinical practice. In this review, we summarize the evidence to date that has informed the thrombosis risk for these agents both in clinical trials and real-world studies. We review data describing the venous and arterial thromboembolic risks in clinical trials of CDK 4/6 inhibitors as well as the now rather extensive real-world evidence available, including a comparison of risk for each of the 3 agents approved for use in breast cancer: palcociclib, ribociclib, and abemaciclib. As the role of prophylactic anticoagulation continues to remain unknown in women receiving CDK 4/6 inhibitors, future efforts directed at carefully investigating the risks and benefits of thromboprophylaxis may lead to improved outcomes in these patients.

Adherence to the CDK 4/6 Inhibitor Palbociclib and Omission of Dose Management Supported by Pharmacometric Modelling as Part of the OpTAT Study

The cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) palbociclib is administered orally and cyclically, causing medication adherence challenges. We evaluated components of adherence to palbociclib, its relationship with pharmacokinetics (PK), and drug-induced neutropenia. Patients with metastatic breast cancer (MBC) receiving palbociclib, delivered in electronic monitors (EM), were randomized 1:1 to an intervention and a control group. The intervention was a 12-month interprofessional medication adherence program (IMAP) along with monthly motivational interviews by a pharmacist. Implementation adherence was compared between groups using generalized estimating equation models, in which covariates were included. Model-based palbociclib PK and neutrophil profiles were simulated under real-life implementation scenarios: (1) optimal, (2) 2 doses omitted and caught up at cycle end. At 6 months, implementation was slightly higher and more stable in the intervention (n = 19) than in the control (n = 19) group, 99.2% and 97.3% (Δ1.95%, 95% CI 1.1−2.9%), respectively. The impact of the intervention was larger in patients diagnosed with MBC for >2 years (Δ3.6%, 95% CI 2.1−5.4%), patients who received >4 cycles before inclusion (Δ3.1%, 95% CI 1.7−4.8%) and patients >65 (Δ2.3%, 95% CI 0.8−3.6%). Simulations showed that 25% of patients had neutropenia grade ≥3 during the next cycle in scenario 1 versus 30% in scenario 2. Education and monitoring of patient CDK4/6i cycle management and adherence along with therapeutic drug monitoring can help clinicians improve prescription and decrease toxicity.

Palbociclib Adherence and Persistence in Patients with Hormone Receptor Positive/Human Epidermal Growth Factor Receptor 2 Negative (HR+/HER2-) Metastatic Breast Cancer

Purpose

To assess adherence and persistence with palbociclib therapy in patients with HR+/HER2- metastatic breast cancer (mBC) in a US real-world setting.

Methods

This retrospective study evaluated palbociclib dosing, adherence, and persistence using commercial and Medicare Advantage with Part D claims data from the Optum Research Database. Adult patients with mBC who had continuous enrollment 12 months prior to mBC diagnosis and initiated first-line palbociclib with aromatase inhibitor (AI) or fulvestrant between 02/03/2015 and 12/31/2019 were included. Demographic and clinical characteristics, palbociclib dosing and dose changes, adherence (medication possession ratio [MPR]), and persistence were measured. Adjusted logistic and Cox regression models were used to examine demographic and clinical factors associated with adherence and discontinuation.

Results

Patients (n = 1066) with a mean age of 66 years were included; 76.1% received first-line palbociclib+AI and 23.9% palbociclib+fulvestrant. Most patients (85.7%) initiated palbociclib at 125 mg/day. Of the 34.0% of patients with a dose reduction, 82.6% reduced from 125 to 100 mg/day. Overall, 80.0% of patients were adherent (MPR), and 38.3% discontinued palbociclib during a mean (SD) follow-up of 16.0 (11.2) and 17.4 (13.4) months, for palbociclib+fulvestrant and palbociclib+AI, respectively. Annual income below $75,000 was significantly associated with poor adherence. Older age (age 65-74 years (hazard ratio [HR] 1.57, 95% CI, 1.06, 2.33), age ≥75 years (HR 1.61, 95% CI: 1.08, 2.41)) and bone-only metastatic disease (HR 1.37, 95% CI, 1.06, 1.76) were significantly associated with palbociclib discontinuation.

Conclusion

In this real-world study, >85% of patients started palbociclib at 125 mg/day and 1 in 3 had dose reductions during the follow-up. Patients were generally adherent and persistent with palbociclib. Older age, bone-only disease, and low-income levels were associated with early discontinuation or non-adherence. Further studies are needed to understand the associations of clinical and economic outcomes with palbociclib adherence and persistence.

Palbociclib with Fulvestrant or Letrozole in Endocrine-Sensitive Patients with HR-Positive/HER2-Negative Advanced Breast Cancer: A Detailed Safety Analysis of the Randomized PARSIFAL Trial

BACKGROUND

Palbociclib has gained a central role in the treatment of hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC). Despite its manageable toxicity profile, venous thromboembolism (VTE) or interstitial lung disease (ILD)/pneumonitis may infrequently occur. Therefore, we provide a comprehensive summary of the safety and tolerability of the combination of endocrine therapy and palbociclib among patients included in the randomized phase 2 PARSIFAL study.

MATERIALS AND METHODS

Patients with endocrine-sensitive HR+/HER2- ABC and no prior therapy in an advanced setting (n = 486) were randomly assigned 1:1 to receive fulvestrant-palbociclib (FP) or letrozole-palbociclib (LP). Laboratory tests and the incidence of adverse events (AEs) were recorded at baseline and day 1 of each cycle. Progression-free survival (PFS) was estimated for patients with and without VTE.

RESULTS

A total of 483 patients were analyzed. Neutropenia, leukopenia, anemia, asthenia, arthralgia, fatigue, and diarrhea were the most frequent AEs in both groups. Febrile neutropenia occurred in 3 (1.2%) patients of the FP group and in 1 (0.4%) patient in the LP group. Six (2.5%; 0.4% grade 3) patients in the FP group and 6 patients (2.5%; 0.4% grade 3) in the LP group experienced ILD/pneumonitis. Pulmonary embolism was reported in 12 (5.0%) patients in the FP group and 6 (2.5%) patients in the LP group. Advanced age at baseline was the only factor significantly associated with an increased risk of pulmonary embolism (P < .01).

CONCLUSION

The PARSIFAL data confirmed the favorable safety profile of both palbociclib regimens. VTE and ILD/pneumonitis were occasionally reported, and their early detection allowed patients to continue treatment effectively without detriment to efficacy.

CLINICALTRIALS.GOV IDENTIFIER

NCT02491983; https://clinicaltrials.gov/ct2/show/NCT02491983).

Real world incidence and management of adverse events in patients with HR+, HER2- metastatic breast cancer receiving CDK4 and 6 inhibitors in a United States community setting

OBJECTIVE

To examine the real-world incidence and management of select adverse events (AEs) among female patients with hormone receptor positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC), receiving a cyclin-dependent kinase 4 and 6 (CDK4 and 6) inhibitor (palbociclib, abemaciclib, or ribociclib).

METHODS

This retrospective study analyzed data from the US Oncology Network iKnowMed electronic health record database for 396 patients with an initial MBC diagnosis on/after 1 January 2014 and receipt of first CDK4 and 6 regimen between 1 January 2017 and 31 December 2018. In this descriptive study, the proportion of patients who experienced select AEs and associated dose modifications or discontinuations were reported. The occurrence of select healthcare resource utilization categories was also reported.

RESULTS

Median follow-up time was 451, 262, and 355 days for patients in the palbociclib, abemaciclib, and ribociclib cohorts, respectively. The most common AEs were neutropenia (palbociclib, 44.8%; abemaciclib, 10.6%; ribociclib, 36.3%), diarrhea (palbociclib, 8.0%; abemaciclib, 43.0%; ribociclib, 8.8%), and fatigue (palbociclib, 12.9%; abemaciclib, 17.6%; ribociclib, 16.5%). AEs resulted in a treatment hold among 91 (23.0%), a dose reduction among 86 (21.7%), and permanent discontinuation among 48 (12.1%) patients overall.

CONCLUSIONS

This real-world study provides insight into the occurrence of AEs which varied by CDK4 and 6 inhibitor. Compared to clinical trials, frequencies of AEs were numerically lower but dose reductions due to AEs were numerically higher. It is possible these differences reflect proactive management of AEs on the part of clinicians to help patients remain on therapy.

Population Pharmacokinetics of Palbociclib and Its Correlation with Clinical Efficacy and Safety in Patients with Advanced Breast Cancer

Neutropenia is the most frequent dose-limiting toxicity reported in patients with metastatic breast cancer receiving palbociclib. The objective of this study was to investigate the pharmacokinetic–pharmacodynamic (PK/PD) relationships for toxicity (i.e., absolute neutrophil count, ANC) and efficacy (i.e., progression-free survival, PFS). A semi-mechanistic PK/PD model was used to predict neutrophils’ time course using a population approach (NONMEM). Influence of demographic and clinical characteristics was evaluated. Cox proportional hazards models were developed to evaluate the influence of palbociclib PK on PFS. A two-compartment model with first-order absorption and a lag time adequately described the 255 palbociclib concentrations provided by 44 patients. The effect of the co-administration of proton-pump inhibitors in fasting conditions increased palbociclib clearance by 56%. None of the tested covariates affected the PD parameters. Model-based simulations confirmed the concentration-dependent and non-cumulative properties of palbociclib-induced neutropenia, reversible after treatment withdrawal. The ANC nadir occurred approximately at day 24 of each cycle. Cox analyses revealed a trend for better PFS with increasing palbociclib exposure in older patients. By characterizing palbociclib-induced neutropenia, this model offers support to clinicians to rationally optimize treatment management through patient-individualized strategies.

The Impact of Real-World Alternative Dosing Strategies of Palbociclib on Progression-Free Survival in Patients with Metastatic Breast Cancer

Background: Palbociclib, a cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitor, in combination with letrozole or fulvestrant has been demonstrated to prolong the progression-free survival (PFS) in patients with hormone receptor-positive (HR+), human epidermal growth factor 2-negative (HER2-) metastatic breast cancer. In efforts to mitigate neutropenic toxicities, oncologists in real-world practice have prescribed alternative dosing strategies with palbociclib, yet the implication on PFS is unknown. Methods: We conducted a retrospective, observational chart review of all female patients at our clinics with HR+, HER2- metastatic breast cancer receiving palbociclib in combination with either letrozole or fulvestrant with a first dose initiated between June 2016 and December 2018 and followed their disease course until 30 April 2020. Results: The median PFS for all clinic patients receiving palbociclib and letrozole (n = 63) was 40.8 months (95% confidence interval (CI) 25.6–not estimable) and 16.97 months (95% CI 8.57–not estimable) for patients receiving palbociclib and fulvestrant (n = 11). We identified seven alternative dosing strategies prescribed by oncologists, the most prevalent being prescribing palbociclib for three weeks on and two weeks off (n = 8). The Kaplan–Meier curves for PFS in patients receiving letrozole and palbociclib prescribed alternative dosing strategies appear to diverge from monograph dosing early in the treatment. Many patients prescribed palbociclib using alternative dosing strategies continued to be observed even by the 18-month timepoint. The prevalence of grade 4 neutropenia was lower for patients on palbociclib with letrozole, suggesting a possible mitigation of severe neutropenia with alternative dosing strategies. Conclusions: We conclude that alternative dosing strategies used by oncologists such as prescribing palbociclib for three weeks on, two weeks off may achieve comparable disease control while mitigating neutropenic toxicities when compared to standard monograph dosing recommendations, prolonging treatment tolerability and adherence. Further large-scale studies are needed to confirm these results for future clinical adoption.

Barriers and facilitators to taking CDK4/6 inhibitors among patients with metastatic breast cancer: a qualitative study

PURPOSE

Most studies of adherence to treatment for breast cancer have focused on early-stage patients. Findings from these studies may not generalize to patients with metastatic breast cancer (MBC). The objective of this study was to identify barriers and facilitators of adherence to cyclin-dependent kinase 4/6 (CDK4/6) inhibitors among patients with MBC, guided by the social ecologic model (SEM).

METHODS

Patients with MBC (N = 25), their caregivers (N = 9), and oncology providers (N = 13) completed semi-structured qualitative interviews exploring their experiences with CDK4/6 inhibitors. Interviews were audio-recorded, transcribed verbatim, and analyzed by three raters using a combined deductive and inductive approach.

RESULTS

Qualitative analysis identified barriers and facilitators of adherence at each SEM level. Intrapersonal and interpersonal factors were most frequently discussed. Intrapersonal factors included knowledge/beliefs about CDK4/6 inhibitors, side effects, and establishing a routine. Interpersonal factors included effective communication with/coordination by the care team, support from family and friends, and information from other patients with MBC. Although less frequently discussed, policy factors (i.e., cost of CDK4/6 inhibitors) were of great concern to patients, caregivers, and providers.

CONCLUSION

Barriers to adherence to CDK4/6 inhibitors exist at multiple levels. Our results underscore the potential value of a multilevel intervention (e.g., patient education, evidence-based strategies for symptom management, tips for open and assertive communication with providers, information about financial resources/support available, and so on) to support adherence in this population.

Risk of venous and arterial thromboembolic events in women with advanced breast cancer treated with CDK 4/6 inhibitors: A systematic review and meta-analysis

BACKGROUND

Cyclin-dependent kinase inhibitors (CDKIs) may increase the risk of thrombotic events of endocrine therapy (ET) in women with hormone-sensitive, HER2-negative advanced breast cancer (BC). Aim of our systematic review is the estimate of the risk of venous and arterial thromboembolism in women with advanced BC treated with CDKIs in phase III randomized controlled trials (RCTs).

METHODS

Studies were identified by electronic search of MEDLINE, EMBASE and CENTRAL database until October 2021. Risk of bias was assessed according to Cochrane criteria. Differences in thrombotic outcomes among groups were expressed as pooled odds ratio (OR) and corresponding 95% confidence interval (CI), which were calculated using both a fixed-effects and a random-effects model. Statistical heterogeneity was evaluated using the I² statistic.

RESULTS

We included 7 phase III RCTs (4415 patients) for a total of 15 papers (7 were the first published paper and 8 the follow-up papers). Reporting of thrombotic events was at high risk of bias. Women with advanced BC treated with CDKIs and ET had a two to threefold increased risk of venous thromboembolic event (VTE) compared to ET plus placebo arm [OR 2.90 (95% CI 1.32, 6.37; I² = 0%) in the main papers and OR 2.20 (95% CI 0.93, 5.20; I² = 49%) in the follow-up papers]. Women with advanced BC treated with CDKIs and ET had a non-significant mild increased risk of arterial thromboembolic event compared to ET plus placebo arm [OR 1.22 (95% CI 0.47, 3.18 I² = 0%)].

CONCLUSIONS

CDKIs in combination with endocrine therapy are associated with a two to threefold higher risk of VTE in comparison to endocrine therapy alone in women with advanced breast cancer, while the risk of arterial events is still to be defined.

Palbociclib dose reductions and the effect on clinical outcomes in patients with advanced breast cancer

BACKGROUND

This study aimed to provide insights into the real-world use of palbociclib, dose reductions, and drug effectiveness in (older) patients with advanced breast cancer (BC).

PATIENTS AND METHODS

Patients with advanced BC treated with palbociclib from 2017 to 2020 were included. The Kaplan-Meier method was used to calculate time to next treatment (TTNT) and overall survival (OS) for patients with or without dose reductions. These clinical outcomes were also compared in subgroup analyses for older patients (≥70 years) and younger patients (<70 years) and for patients discontinuing palbociclib early (<4 administrations).

RESULTS

A total of 598 patients with advanced BC were included, with a median age of 64 years. Palbociclib dose reductions occurred in 33% of all patients. Early discontinuation of palbociclib without dose reductions occurred in 23% of the patients. Patients who required a palbociclib dose reduction were older (median age 67 years vs. 63 years). Patients with dose reductions had a significantly higher TTNT of 16.9 vs. 11.4 months (p < 0.001) and median OS of 29.7 vs. 21.9 months (p = 0.003) compared to patients without dose reductions. The TTNT in older patients was significantly longer (16.9 vs. 11.6 months, p = 0.013) than younger patients, but OS was similar (20.7 vs. 26.7 months, p = 0.051).

CONCLUSION

Palbociclib dose reductions occurred in real-world practice similarly to the PALOMA-3 trial. Patients with dose reductions had no poorer outcomes compared to patients not requiring a dose reduction. Older patients treated with palbociclib had more frequent dose reductions, but this did not appear to affect OS.

Palbociclib as an early-line treatment for Japanese patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer: a review of clinical trial and real-world data

Breast cancer is the most common type of cancer among women worldwide and in Japan. The majority of breast cancers are hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2‒), and endocrine therapy is an effective therapy for this type of breast cancer. However, recent substantial advances have been made in the management of HR+/HER2‒ advanced breast cancer (ABC) with the advent of targeted therapies, such as cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, resulting in significant improvements in survival outcomes versus endocrine therapy alone. To evaluate the optimal use of palbociclib, a CDK4/6 inhibitor, in HR+/HER2- ABC, this review summarizes clinical trial and real-world data for palbociclib. In addition, current biomarker studies in palbociclib clinical research are reviewed. In Japanese patients, palbociclib was shown to be effective with a manageable safety profile, although differences were observed in the frequency of adverse event and dosing parameters. Current evidence supporting palbociclib as a first-line treatment strategy for patients with HR+/HER2‒ ABC in Asia, and specifically japan, is also discussed.

Association between cyclin-dependent kinase 4/6 inhibitors and venous thromboembolism: analysis of F.A.E.R.S. data

Objectives:Real world studies have started to emerged on occurrence of venous thromboembolism (VTE) with cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors, but still deserve constant surveillance and evaluation. This study was to analyze this association. Methods: Adverse event cases were acquired from the US Food and Drug Administration Adverse Event Reporting System (FAERS) database betweenJanuary 1st 2015 and December 31st 2020.Signals indicating association between CDK 4/6 inhibitors and VTE were identified by reporting odds ratio (ROR). Results: CDK 4/6 inhibitors had a total of 631 reports of VTE (ROR 1.44, 95% CI 1.33-1.55) compared with non-CDK 4/6 inhibitors. Palbociclib (ROR 1.42, 95% CI 1.09-1.88) demonstratedthe highest number of VTE reports, followed by ribociclib (ROR 1.41, 95% CI 1.29-1.54) and abemaciclib (ROR 0.92, 95% CI 0.72-1.17). Conclusions:Although it is not able to confirm the casual relationship between VTE and CDK4/6 inhibitors, this study suggested signal of VTE reporting in patients receiving CDK4/6 inhibitors, which is likely to reflect a potential association. The results may enhance physicians' awareness of the potential side effect of VTE associated with CDK 4/6 inhibitors. An early recognition of VTE signs/symptoms could decrease the morbidity and severity of such adverse events.

Real-world clinical outcome and toxicity data and economic aspects in patients with advanced breast cancer treated with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors combined with endocrine therapy: the experience of the Hellenic Cooperative Oncology Group

Background

We evaluated real-world clinical outcomes and toxicity data and assessed treatment-related costs in patients with advanced breast cancer who received treatment with cyclin-dependent kinase inhibitors (CDKi).

Patients and methods

We conducted a prospective–retrospective analysis of patients with advanced hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer who received a CDKi, in combination with endocrine therapy, at any line of treatment. The primary endpoint was progression-free survival (PFS). Cost analysis was conducted from a public third-payer (National Organization for Healthcare Services Provision (EOPYY)) perspective, assessing only costs related to direct medical care, including drug therapy costs and adverse drug reaction (ADR)-related costs.

Results

From July 2015 to October 2019, 365 women received endocrine therapy combined with CDKi; median age was 61 years, postmenopausal 290 (80.6%) patients. CDKi were administered as first-line treatment in 149 (40.9%) patients, second-line treatment in 96 (26.4%) and third-line treatment and beyond in 119 (32.7%) patients. The most common adverse events were neutropenia, anaemia, thrombocytopenia and fatigue. Grade 3–4 adverse events occurred in 86 (23.6%) patients, whereas 8 (2.2%) patients permanently discontinued treatment due to toxicity. The median PFS for patients who received CDKi as first-line, second-line and third-line treatment and beyond was 18.7, 12 and 7.4 months, respectively. The median overall survival since the initiation of CDKi treatment was 29.9 months (95% CI: 23.0–not yet reached (NR)). The mean pharmaceutical therapy cost estimated per cycle was 2 724.12 € for each patient, whereas the main driver of the ADR-related costs was haematological adverse events.

Conclusions

Treatment with CDKi was well tolerated, with a low drug discontinuation rate. Patients who received CDKi as first-line treatment had improved PFS and OS compared with second-line treatment and beyond. The main component of direct medical costs assessed in the cost analysis comprises CDKi pharmaceutical therapy costs.

Trial registration number

NCT04133207

Phase I-II Open-Label Multicenter Study of Palbociclib + Vemurafenib in BRAF V600MUT Metastatic Melanoma Patients: Uncovering CHEK2 as a Major Response Mechanism

PURPOSE

In BRAF ^V600MUT metastatic melanoma, cyclin D-CDK4/6-INK4-Rb pathway alterations are involved in resistance to MAPK inhibitors, suggesting a clinical benefit of cyclin-dependent kinase 4 (CDK4) inhibitors. In this phase I-II study, we aimed to establish the MTD of palbociclib when added to vemurafenib.

PATIENTS AND METHODS

Patients with BRAF ^V600E/KMUT metastatic melanoma harboring CDKN2A loss and RB1 expression were included and stratified into two groups according to previous BRAF inhibitor treatment (no:strata 1; yes:strata 2). Treatment comprised palbociclib once daily for 14 days followed by a 7-day break + continuous dosing of vemurafenib. The primary endpoint was the occurrence of dose-limiting toxicity (DLT), and the secondary endpoints included the best response, survival, pharmacokinetics, and tumor molecular profiling.

RESULTS

Eighteen patients were enrolled, with 15 in strata 2. Characteristics at inclusion were American Joint Committee on Cancer stage IVM1c (N = 16; 88.9%), high lactate dehydrogenase (N = 9; 50.0%), and median number of previous treatments of 2. One and 5 patients experienced DLT in strata 1 and 2, respectively, defining the MTD at palbociclib 25 mg and vemurafenib 960 mg in strata 2. No significant evidence for drug-drug interactions was highlighted. The median progression-free survival was 2.8 months, and 5 (27.8%) patients showed a clinical response. The baseline differential mRNA expression analysis and in vitro data revealed the role of CHEK2 in the response to palbociclib.

CONCLUSIONS

Although the combination of palbociclib + fixed-dose vemurafenib did not allow an increased palbociclib dosage above 25 mg, a significant clinical benefit was achieved in pretreated patients with melanoma. An association between the transcriptomic data and clinical response was highlighted.

Use of molecular targeted therapy for hormone receptor-positive, human epidermal growth factor 2-negative metastatic breast cancer in real-world clinical practice

BACKGROUND

The emergence of molecular targeted therapies (MTTs) has altered the treatment landscape of hormone receptor-positive (HR+), human epidermal growth factor 2-negative (HER2-) metastatic breast cancer (MBC). The objective of this study was to describe treatment patterns, clinical outcomes, and safety profiles among patients with HR+/HER2- MBC treated with palbociclib, abemaciclib, or everolimus in a clinical practice setting.

METHODS

Forty-five patients with HR+/HER2- MBC were enrolled; of these, 40 received molecular targeted therapy (MTT) in ≥3^rd lines and 5 received treatment in the 1^st/2^nd line. The results were compared with clinical trials.

RESULTS

Median progression-free survival (PFS) in all patients was 5.3 months (95% confidence interval [CI] 2.8-8.4), and a similar PFS was found for patients receiving 1^st/2^nd line (5.5 months, 95% CI 1.8- ) and ≥ 3^rd line (5.1 months, 95% CI 2.8-9.4) treatments. Eleven patients continued with the same regimen for >1 year; treatment is ongoing for 15 patients. In 23 patients (51%), everolimus was administered prior to cyclin-dependent kinase (CDK) 4/6 inhibitors. The most frequent grade 3 or higher adverse event (AE) with CDK4/6 inhibitors was neutropenia, whereas AEs ≥ grade 3 with everolimus included Pneumocystis pneumonia, sepsis, and stomatitis.

CONCLUSIONS

Molecular targeted therapy (MTT) was mostly used in ≥ 3^rd lines, and PFS of patients receiving 1^st/2^nd line and ≥ 3^rd line treatments was similar; however, this study included heavily treated patients and a limited number of cases. Treatment options should take into consideration the maximal benefit to the patient based on the results of clinical trials.

Ribociclib Population Pharmacokinetics and Pharmacokinetic/Pharmacodynamic Analysis of Neutrophils in Cancer Patients

The population pharmacokinetics (popPK) of ribociclib and population pharmacokinetic/pharmacodynamic (PK/PD) relationship between ribociclib and absolute neutrophil count (ANC) were characterized in patients with cancer. PopPK and ANC PK/PD modeling were both conducted in 2 rounds per data availability. Initial models were developed based on data sets from early-phase trials and qualified using external data from the phase III MONALEESA-2 trial. The second round of analyses was performed using updated data sets that included 2 more phase III trials (MONALEESA-3 and -7). The popPK and ANC PK/PD models adequately described the data and demonstrated reasonable predictive ability. Covariate analysis showed that ribociclib PK were not affected by age, sex, race, baseline Eastern Cooperative Oncology Group (ECOG) status (grade 1), mild/moderate renal impairment, mild hepatic impairment, or concomitant use of combination partners, including aromatase inhibitors (letrozole, anastrozole) or fulvestrant, proton-pump inhibitors, or weak cytochrome P450 3A4/5 inhibitors. Body weight had no impact on ribociclib clearance to warrant dose adjustment. The ANC PK/PD relationship was not affected by age, weight, sex, race, baseline ECOG status (grade 1), or concomitant use of letrozole, anastrozole, or fulvestrant. The PK/PD analysis confirmed reversibility of ribociclib's effect on ANC; it also suggested that lowering the dose of ribociclib would mitigate ANC decrease and neutropenia risk. The popPK and ANC PK/PD analyses support the use of ribociclib in combination with an aromatase inhibitor or fulvestrant in patients with hormone receptor-positive, human epidermal growth factor receptor-2-negative advanced or metastatic breast cancer without dose adjustment in subpopulations, and the use of dose interruption/reduction to mitigate potential treatment-emergent neutropenia.

Thromboembolic Events with Cyclin-Dependent Kinase 4/6 Inhibitors in the FDA Adverse Event Reporting System

Simple Summary

This post-marketing research addressed the role of cyclin-dependent kinase 4/6 inhibitors, relatively new anticancer drugs approved for advanced breast cancer in cancer-associated thrombosis. We used the Food and Drug Administration pharmacovigilance database to retrospectively assess thromboembolic events in the real world. A potential class effect was found for venous thrombosis, whereas distinctive arterial events emerged for ribociclib. These signals call for both prospective research and early proactive monitoring by oncologists, also in patients without apparent risk factors. These findings strengthen the role of timely pharmacovigilance to detect and characterize post-marketing adverse events of special interest, thus supporting patient care.

Abstract

We analyzed thromboembolic events, recognized (AESIs), with cyclin-dependent kinase (CDK)4/6 inhibitors, using the Food and Drug Administration adverse event reporting system. Methods: Thromboembolic events were characterized in terms of spectrum [venous and arterial thromboembolism (VTE; ATE)] and clinical features by combining the disproportionality approach [reporting odds ratio (ROR) with 95% confidence interval (CI)] with individual case assessment. Results: A total of 1722 thromboembolic events were retained. Increased VTE reporting emerged for CDK4/6 inhibitors in the exploratory analyses (n = 659; ROR = 1.51; 95% CI = 1.39–1.63), with consistent disproportionality in the consolidated analyses (e.g., deep vein thrombosis with abemaciclib: 17; 1.98; 1.22–3.19). Higher-than-expected ATE reporting was found for ribociclib, including myocardial infarction (41; 1.82; 1.33–2.48), with rapid onset (median latency 1 vs. 6 months for other CDK4/6 inhibitors). Causality was highly probable or probable in 83.2% of cases, with a negligible proportion of pre-existing drug- and patient-related risk factors except for cardiovascular comorbidities (26%). Conclusions: Although causal association cannot be firmly inferred, oncologists should proactively monitor the occurrence of VTE with CDK4/6 inhibitors. The unexpected distinctive increased ATE reporting with ribociclib deserves urgent clarification though large comparative population-based studies. We support pharmacovigilance for the post-marketing characterization of AESIs, thus promoting real-time safe prescribing in oncology.

CDK4/6 inhibitors in breast cancer: differences in toxicity profiles and impact on agent choice. A systematic review and meta-analysis

Introduction: CDK4/6 inhibitor approval for hormone-responsive breast tumors has significantly changed therapeutic algorithms, with three drugs currently approved.Areas covered: Here, we analyze the toxicity profiles of palbociclib, ribociclib, and abemaciclib through a systematic review and meta-analysis. Palbociclib and ribociclib showed high rates of hematological toxicity, primarily neutropenia, and were associated with a low rate of severe infections. Abemaciclib was associated with a high rate of gastrointestinal toxicities, primarily diarrhea, of grade 1-2 in most cases. Ribociclib was associated with a high rate of hepatic, and respiratory toxicity and with QTc prolongation. The toxicity rate of ribociclib was higher in metastatic patients than non-metastatic patients, with approximately 33% more grade 3-4 toxicities and 21% more grade 3-4 neutropenic events. A 5% higher risk of diarrhea was observed in postmenopausal patients. Pre-treated patients did not show a higher toxicity rate for palbociclib/ribociclib than previously untreated patients, while a 26% higher risk of any grade neutropenia and 6% higher risk of grade 3-4 diarrhea were observed with abemaciclib.Expert opinion: Considering the similar efficacies and indications of palbociclib, ribociclib, and abemaciclib, the evaluation of their toxicity profiles may facilitate treatment choice.

Real life efficacy of palbociclib and endocrine therapy in HR positive, HER2 negative advanced breast cancer

BACKGROUND

Palbociclib is indicated for the treatment of hormone receptor-positive (HR+), HER2-negative (HER2-) advanced breast cancer (ABC), in combination with endocrine therapy. Emerging real-life data suggest that the efficacy of a palbociclib-based therapy is highly conserved. We report the Institut Curie hospital experience.

PATIENTS AND METHODS

We retrospectively reviewed all patients with HR + HER2- ABC treated with a palbociclib-based therapy as first or second line for ABC, with an initial prescription from November 2016 to December 2018. Clinical, laboratory and imaging data were retrieved from electronic records. Data lock was December 31st, 2019. Descriptive analyses, univariate and multivariate Cox regression analyses were performed.

RESULTS

We included 310 consecutive patients. Median age was 61.8 years old. Palbociclib was prescribed in first line in 225 patients (72.6%). Before palbociclib-based therapy initiation, 122 patients (39.3%) were endocrine naive, 96 (31.0%) endocrine sensitive and 92 (29.7%) endocrine resistant. Median follow-up was 20.7 months. Median progression free survival (PFS) was 23.4 months (95%CI: 21.6-NR) in endocrine naive patients, 22.7 months (95%CI: 14.7-NR) in endocrine sensitive, and 13.4 months (95%CI: 10.7-20.8) in endocrine resistant. At 12 months from the initiation of palbociclib, 94.5% of patients were alive. By multivariate analysis, poor prognosis factors for PFS were identified in the endocrine naive/sensitive population: initial ECOG status 2, previous endocrine therapy for ABC, 3 metastatic sites or more. Toxicity profile was similar to previously published data.

CONCLUSION

In a non-selected population of patients with HR + HER2- ABC, the efficacy and safety data are strikingly similar to those previously reported.

Real-World Clinical and Economic Outcomes Associated with Palbociclib for HR-Positive/HER2 Negative Metastatic Breast Cancer: A Commentary

Despite the achieved advancement in pharmacological cancer treatments, the majority of postmenopausal women with hormone receptor-positive metastatic breast cancer (mBC) will experience disease progression. Research into alternative therapies with improved efficacy and reduced side effects has led to the development of a new class of oral anticancer medications, the cyclin-dependent kinase (CDK) 4/6 inhibitors, which include palbociclib, ribociclib, and abemaciclib. Nonetheless, there is growing evidence that the effectiveness of oral anticancer medications is sub-optimal, being influenced by low adherence, sociodemographic factors, and adverse effect profiles. In addition, there is a disconnect between the high price tags of CDK 4/6 inhibitors and their observed effectiveness, raising questions about their value. Currently, the existing knowledge base on the effectiveness and cost-effectiveness of newer oral anticancer medications in understudied populations with possible health disparities is scant. This commentary discusses what is known about palbociclib's clinical effectiveness, safety, and adherence and suggests the need for further studies of real-world effectiveness and cost-effectiveness to help establish the value of newer oncologic drugs, such as palbociclib. DISCLOSURES: No funding supported the writing of this article. The authors have nothing to disclose.

Palbociclib use with grade 3 neutropenia in hormone receptor-positive metastatic breast cancer

PURPOSE

Neutropenia is the most common toxicity of CDK4/6 inhibitors, causing frequent dose interruptions. However, CDK4/6 inhibitor-induced neutropenia shows a benign clinical course in contrast to that caused by chemotherapy. Here, we investigated the safety of a new dose scheme for palbociclib, which avoids dose delays or reductions due to afebrile grade 3 neutropenia.

METHODS

A consecutive cohort of ER( +)/HER2( -) advanced breast cancer patients who received palbociclib between 2017 and 2018 was analyzed. The patients were classified into Group 1 (patients who maintained palbociclib dose with afebrile grade 3 neutropenia), Group 2 (patients who experienced any dose modification with afebrile grade 3 neutropenia), and Group 3 (patients without afebrile grade 3 neutropenia). The primary endpoint was febrile neutropenia incidence; other toxicities were compared with those of the PALOMA-2 trial.

RESULTS

Among the 107 patients, 54.2%, 22.4%, and 23.4% were classified into Groups 1, 2, and 3, respectively. There was no febrile neutropenia in Groups 1 and 2 during palbociclib treatment. Group 1 showed higher incidence of thrombocytopenia (all-grade, 32.8%; grade 3-4, 8.6%) than Group 2 and the PALOMA-2 data, but there was no bleeding related to thrombocytopenia. Group 1 showed higher incidence of all-grade non-hematologic adverse events than Group 2; only one grade 3 non-hematologic toxicity was observed in Group 1. There were no treatment-related hospitalizations or deaths in Group 1.

CONCLUSIONS

Thus, omitting palbociclib dose modification with afebrile grade 3 neutropenia is safe and tolerable without febrile neutropenia events. This scheme could be useful to avoid unnecessary reductions in palbociclib doses in future practice.

Venous thromboembolism in breast cancer patients receiving cyclin-dependent kinase inhibitors

BACKGROUND

Venous thromboembolism (VTE) complicates several anticancer regimens including chemotherapy and antiangiogenic agents. Cyclin-dependent kinase inhibitors (CDKIs) are a new approach for hormone receptor-positive metastatic breast cancer (mBC). Reported VTE rates in randomized trials range from 0.6% to 5%, but these may underestimate actual rates observed in clinical practice.

OBJECTIVES

Evaluate VTE rate and its association with outcomes in CDKIs patients.

PATIENTS/METHODS

We conducted a retrospective cohort study of consecutive mBC patients who received any of three Food and Drug Administration (FDA)-approved CDKIs (palbociclib, ribociclib, abemaciclib) from January 2015 through December 2017. Venous thromboembolism including deep venous thrombosis (DVT), pulmonary embolism (PE), and visceral vein thrombosis (VVT) were identified by electronic medical record review. Overall survival (OS) and progression-free survival (PFS) were estimated and evaluated for association with VTE using Cox proportional hazard regression.

RESULTS

We included 424 patients, with a median age at diagnosis of 55 years. Palbociclib was the most commonly used CDKI (n = 390, 91.8%). Venous thromboembolism during CDKIs occurred in 38 patients, 6.3% at year 1, including DVT in 52.6%, PE in 18.5%, and VVT in 15.8%. Median time to VTE was 314 days. Venous thromboembolism was associated with a trend to worse PFS and OS in multivariate analysis [PFS hazard ratio (HR) 1.40, 95% confidence interval (CI) 0.83-2.38, P = .21], OS (HR 1.70, 95% CI 0.95-2.98, P = .076).

CONCLUSIONS

Venous thromboembolism rates with CDKI treatment in mBC in clinical practice are 2-fold to 5-fold greater than reported in registration trials and may be associated with worse outcomes.

Palbociclib in metastatic breast cancer: current evidence and real-life data

The purpose of this review is to summarize the background and latest evidence for the use of palbociclib, an oral, first-in-class, highly selective cyclin-dependent kinase 4/6 inhibitor, in advanced breast cancer, with a focus on some of the unanswered questions about the performance of this agent in clinical practice. The available clinical data from both controlled clinical trials and real-life experiences concerning palbociclib-based combinations in patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) metastatic disease, including patient-reported outcomes and subgroup analyses, have been reviewed and discussed. Palbociclib significantly improved progression-free survival and clinical benefit rates when added to letrozole in postmenopausal women as initial endocrine-based therapy, and it prolonged progression-free survival and overall survival when added to fulvestrant in women who progressed on previous endocrine therapy in randomized clinical trials. Tolerability profile was manageable, with neutropenia occurring most commonly, without detrimental impact on quality of life. Available data from real-life experiences confirm the good performance of palbociclib in unselected, heavily pretreated populations. Palbociclib in combination with endocrine therapy is a valuable emerging option for patients with HR+/HER2- advanced or metastatic breast cancer. Further investigation is needed to provide solutions for palbociclib resistance and to identify the best sequence to use for the best patient benefit with a minimal toxicity.